Polymer sheets that can be used as interlayers in light-transmitting, multiple layer laminates, such as safety glass or polymeric laminates, typically comprise poly(vinyl butyral). Safety glass generally refers to a transparent laminate comprising a poly(vinyl butyral) sheet disposed between two panes of glass. Safety glass often is used to provide a transparent or decorative barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening.
Although poly(vinyl butyral) is well suited in general for use as a polymer sheet in safety glass interlayers, alternative materials are often useful as well. For example, poly(ethylene-co-vinyl acetate) (EVA) and polyurethane have both been used as interlayers in glazing laminates. Interlayer materials are chosen for, among other reasons, improved handling, reduced cost of production, and improved performance. Alternatives to poly(vinyl butyral) interlayers could be useful, for example, if those alternatives showed improved performance below 0° C. and/or above 35° C., where standard poly(vinyl butyral) has relatively poor impact performance. Furthermore, alternatives which could provide much higher penetration resistance and stiffness to the laminated glass will be desired as well in applications requiring high security, bullet-proofing, hurricane-proofing, glazing, and so on.
Accordingly, further improved materials for use as an interlayer or part of an interlayer in multiple layer glass panels are needed in the art.